The long-range goals of this work are to determine the mechanisms of cellular motility in normal and transformed cells. We will test directly whether or not the contractile proteins have a role in force production for cellular motility. Our approach is to produce specific antibody inhibitors of contractile protein function, to microinject them into living cells and to analyze their effects on cell locomotion, chromosome movement in mitosis and cytokinesis. In this way, we can evaluate whether or not contractile protein function is among the phenotypic changes that distinguish normal from transformed cells. These experiments provide a direct test for the relevance of the morphological changes in the distribution of the contractile proteins observed upon transformation. Four manuscripts have been submitted, which describe the production, purification and characterization of a library of 30 monoclonal antibodies to myosin-II, isolated from Acanthamoeba. Among the antibodies were approximately 12 that had profound effects on myosin function: some antibodies blocked actomyosin ATPase activity, others contraction of cytoplasmic gels and still others myosin filament formation. The effects were specific and required antibody in 1:1 molar equivalence with myosin. Electron microscopy of platinum-shadowed antibody-myosin complexes in conjunction with detailed analysis of antibody effects on myosin function has provided insight into how the molecular structure of myosin is related to the mechanism by which myosin transduces chemical energy into mechanical force. We have made excellent progress on the production of monoclonal antibodies to human platelet myosin. Antibody PM-1 specifically recognizes platelet myosin heavy chain and cross-reacts with cytoplasmic myosins from a variety of cultured cell lines. We are currently engaged in evaluating the effects of these antibodies on platelet myosin function. In addition we are currently perfecting the methods required for microinjection of these proteins into amoebas and into cultured mammalian cells. This approach, the development of customized inhibitors of contractile protein function in vitro and their subsequent injection into living cells, is currently the most direct and possibly the only way to relate our current understanding of the biochemical properties of the nonmuscle contractile proteins to the numerous and complex interactions that give rise to motility in living cells.